Can a generator be connected to a 220v outlet to provide emergency power for a house?

Question

If an electric generator with 220v single phase output is connected to a home electrical system through a 220v outlet and the main breaker in the breaker box is turned off to disconnect the house from the city power, will the generator then power the house without feeding power back to the city power grid?

Could an existing outlet be used, such as an electric dryer outlet, if the load from the house was first adjusted to ensure that it was less than the breaker capacity on the dryer outlet?

What are the dangers to doing this (aside from those related directly to generating your own power)?

What is the correct way to do this without spending a thousand or more dollars on automatic transfer switches and such?

The house in question has 200A service and would be provided with a 12kW generator. Most lighting is CF so excepting appliances normal power usage profile for the house is well within the generators capacity.

When running on emergency power major power consuming appliances (ovens, stove, dryer, AC) would not be used or would be engaged only after ensuring that sufficient capacity was available.

Answer 1

First your 220VAC generator most likely has a neutral as well. So you really are producing 2 phase 110VAC.

Next 20Amp x 220VAC = 4.4KW which is your power limit for back feeding through the dryer outlet.

On a side note your power company uses transformers to step down high voltage into a lower voltage for your house. Transformers work in BOTH directions , the voltage from your generator can backfeed to the local transformer and be stepped up to a higher voltage.

As mentioned in a previous response this is HOW someone could be killed or injured working on a line that did not have power on it prior to your connecting your generator.

The remedy for this is to disconnect the main breaker. But people forget to do that so a transfer switch is added. The transfer switch is wired so that power to your house may only come from either the generator OR the power lines. It is designed to prevent cross connection and back feeding and most likely your local code will require one to be installed.

You only need and automatic transfer switch if you have a generator which will auto start on a power failure. manual transfers are much cheaper. (See Northern Tool web site)

Another problem encountered when back feeding is that it is easy to overload the generator. Again people forget details in an emergency. You have to switch off non essential circuit breakers and strip down the load on your pannel prior to powering from the generator. Too much load on the gen will stress its windings and pop the 20 amp circuit breaker.

The transfer switch not only disconnects the power grid from yur gen but only allows power to a dedicated group of hi priority breakers such as your heater, well pump ect...

Answer 2

This Site Might Help You.

RE:
Can a generator be connected to a 220v outlet to provide emergency power for a house?
If an electric generator with 220v single phase output is connected to a home electrical system through a 220v outlet and the main breaker in the breaker box is turned off to disconnect the house from the city power, will the generator then power the house without feeding power back to the city...

Answer 3

there are solar generators .. basically build it yourself .. you need a battery bank, a charger, and an inverter sized according to your needs. As mentioned above it wont go as far as you might think and designing a backup system around conservation is going to be key to success. There is alot you should research and learn about batterys, what voltage you want to design a battery bank for, and matching an inverter and charger to the system ... to give you an idea of an 'overnight' system which wouldnt power an ac or dryer or 240 hot water heater .. you would need about 8 210AH golfcart batterys, a 2500 watt pure sine inverter, about a 40 amp charger minimum (and know how to charge properly if its not automatic) and you could conceivable run a purpose designed well water system, run a few low wattage lights, run a laptop, maybe cook a quick meal on a low power mic or induction hotplate, and run a fan or two or a heated blanket .... if you wanted hot water off the grid you would have to plan that likely to be heated on the genset .. and of course you need the genset ... this is basically a solar system without the panels using a generator instead ... easily you could get 4-5 grand into something functional ...

Answer 4

What you propose will work perfectly fine. The reason that it is discouraged through code sections and even subsequent answerer's below is that it is prone to error with extreme consequences.
Believe it or not there may be some unknowing person out there or even a forgetful one that could make a fatal mistake. It sounds like you know what you are doing just don't make a mistake and you didn't hear it from me.
The dangers are:
Killing a lineman on the pole down the street
Killing your neighbor.
Yourself and family members
Local fire and explosion.

If we don't see it in the paper we will know you did it right.

Answer 5

Your current will be limited by the breaker you are feeding the house with. Instead of running through a 100 amp main, you will be running back through a 20 amp dryer breaker.

Yes, this could work. You are limited by your dryer breaker amperage. Don't buy too big a generator - you won't be able to use it.

The expense of "automatic transfer switches" is the "automatic" part, not the "transfer" part. Use a manual switch and manually start your generator. That rig should be less.

Answer 6

Two problems; 1. Too much juice going into the house. The 110 outlets and appliances will NOT like it! 2. Most likely the juice will not flow back into any line OTHER than back to the breaker box. Either way, this may cause serious damage to your wiring.

I have one of those standby generators. Let me say get ready for a FIGHT to get it installed! It took me 7 MONTHS and weekly fights with the generator company, home depot, the gas company, the city and the permits to get it finally done. Mine cost about $3,800. I got a 5 year loan to pay for it.

Answer 7

it could power some things but what about the amps. How much are you trying to run? Theoretically possible but would have to be a very small house.

Answer 8

Yes to all questions

Answer 9

yes